Rust-preventing compounds



Patented June 28, 1949 RUST-PREVENTIN G COMPOUNDS Jones I. Wasson and John C. Zimmer, Union, N. J

assignors to Standard Oil Development Company, a corporation of Delaware No Drawing. Application June 11, 1947, Serial No. 754,085

6 Claims.

1 This invention relates to rust preventing compounds and particularly to mineral oil rust preventives containing rust inhibitor additives which are highly efiective in small concentration.

In the patent to Rosen, No. 2,216,751, there is described a method of making thioether substituted monobasic organic acids which have been found useful, as mentioned in said patent, for various purposes such as drying accelerators, for linseed oil and related material, for use in the formation of heavy metal soaps and the like. The patent referred to covers a number of compounds, some of which include complex alkyl radicals. The higher members of this class are moderately soluble in mineral oil but the lower members, for example those having less than about 12 carbon atoms in the alkyl radical, are only slightly soluble.

Compounds of the character just referred to, and particularly the lower compounds, have been found to be efiective to some degree as rust inhibitors when added to mineral oil. Due to their low solubility in oil, however, they are not very effective by themselves and a purpose of the present invention is to improve their effectiveness.

We have discovered that by combining alkyl thioethers of acids of the type referred to above, namely the lower thioether substituted monobasic organic acids, with a small amount of certain esters of polyhydric alcohols, the rust preventing qualities of these acids can be considerably enhanced. By this means, even though the acids are only very slightly soluble, they may be successfully employed as inhibitors within their solubility limits. The combination of such thioethers of acids with the esters referred to appears to impart unusual rust inhibiting properties to oil solutions containing such materials. The combination of small amounts of these ingredients appears to be considerably more effec tive in preventing rust of ferrous metals than would be expected from a consideratipnof the properties of either compound by itself. In effect the rust preventing characteristics of its small quantities of thioether substituted monobasic organic acids appears to be multiplied several times by combination with similar amounts, or amounts generally of the same order, of polyhydric alcohol esters. I

Specifically we have found that alkyl thioethers of certain compounds, where the etherifying group is attached to a carbon atom of a carboxylic acid outside the carboxyl group, such as 11 alkyl thio acetic acid, alkyl thio propionic acid and related straight chain materials not higher than butyric acid derivatives possess the desired rust inhibiting properties mentioned above. It appears that if suflicient quantities of these materials could be dissolved in mineral oils, they might be themselves quite satisfactory for preventing rust in the presence of water. Due to their low solubility in mineral oil, however, it has been found necessary to supplement or augment their inhibiting effect as indicated above. The alkyl components of the acids just referred to may be straight or branched chain radicals, or they may be alicyclic or alkaryl, provided that the resulting compounds have at least a small degree of oil solubility. As in other related compounds, oil solubility appears to bear a relation to the length of the alkyl chain. More specifically, compounds such as decyl or dodecyl a thio acetic acid, or 13 decyl thio propionic acid and compounds of the same general type and order are satisfactory.

In general, the compounds referred to may have the following formula, R-S-(CHz) x-COOH, wherein R is a hydrocarbon radical having preferably 10 or more carbon atoms, not more than about 24, and X is an integer having a value of from 1 to 6. Acids of this type may be prepared by reacting the sodium salt of an alpha, beta, etc., halogen substituted organic acid with sodium mercaptide in an alcohol-water solvent in accordance with the following reactions:

11 Hemadecyl thio acetic acid Mono chloro acetic acid sodium salt ClCHzCOONa+CmHaaSNa- C16Ha3SCH2COONa+NaCl C16H33SCHzCOONa-FHCl-KZwI-IaaSCHzCOOH (a cetyl thio acetic acid) 1 Esters which are suitable for combining with these acids, as described hereinabove, preferably. include the esters, or partial esters, of common polyhydric alcohols and any suitable organic acid. Apparently the esters of any suitable polyhydric alcohol and any suitable acid may be used with satisfactory results. For example, the esters of ethylene and polyethylene glycol, glycerol and the like formed with higher acids such as oleic acid. ricinoleic acid, naphthenic acids, and other related compounds of the same general character are quite satisfactory. Ricinoleic acid which is a major constituent of castor oil has been found to be quite satisfactory for this purpose.

Other esters than those listed above ma be used if desired. For example, the monooleate or dioleate of pentaerythritol and various analogous derivatives of sorbitol may be employed. Further specific examples are sorbitan mono- Cetyl mercaptide laurate (sorbitan being a partially dehydrated sorbitol), sorbitan mono-palmitate, or the corresponding monostearate, monooleate, or trioleate, ester, or the polyoxyalkalene derivatives of any of these sorbitol esters. These compounds have surface active properties, being compatible in varying degrees with both water and oil and these properties make them desirable constituents of rust preventing compositions since they insure intimate contact between the oil and the surface to be protected.

We have found that catalysts are commonly required for the preparation of esters of the type referred to above. When conventiona1 acid catalysts are used in their preparation, it is frequently dimcult to wash out all of the catalyst and a small part thereof commonly remains in the ester. Since the presence of a free acid catalyst in the finished product would be quite objectionable when the compound is intended to be used for rust inhibiting purposes, it is desirable either to completely remove the free catalyst or to neutralize it. We have found it to be simpler and entirely satisfactory to neutralize the free acidity in the ester with a suit- It will be noted that heavy rust was obtained on the steel test piece with uninhibited turbine oil. With the same turbine 01 containing small quantities of a cetyl thio acetic or polyethylene glycol hexaricinoleate used separately, a light rust was formed. Increasing the concentration of the individual additives, when used singly, did not 011. With the same turbine oil containing small little or no improvement being shown. The additive alkyl thio acid proved to be too insoluble when used alone in amounts which apparently would be necessary to pass the ASTM rust test with synthetic sea water. Furthermore, the ASTM rust test was not successfully passed and excessive emulsion was formed when the polyethylene glycol hexaricinoleate was used alone, though in substantially larger amounts. On the other hand, the same turbine oil with 0.03% a cetyl thio acetic acid plus 0.1% of the ester entirely prevented the formation of rust according to data obtained in the foregoing test.

The results of adding additional quantities of the ester and acid in an attempt to successfully inhibit rust by the use of single compounds are shown in the following table:

Navy Emulsion Test at 130 F. ASTM Rust Test With Synthetic Sea Water Remarks Distilled 1'7 NaOl Water 0 Solution Turbine 0 +0E1% Polyethylene Glycol Hexaricinole- +0.t2% Polyethylene Glycol Hexaricinole- 8 +0.03'7 Cetyl thio acetic acid 9 Cetyl thio acetic acid Trace." do.

Trace Light Rust .do, do Excessive Emulsion.

. do. do

Not all soluble.

l Solvent extracted Mid-Continent oil of 190 S. S. U. vis./lF., 107 V. I.

able basic material such as a basic amine. A small amount of phenyl ethanol amine is an example of a material satisfactory for this purpose. When this is done, the neutralized product, that is the ester containing a minor amount of neutralized acid catalyst, may be combined with the thioether organic acids described hereinabove without further refinement and will be found to be entirely satisfactory for rust inhibiting purses. Other alkaline materials which are suitable for the purpose of neutralizing free acid catalyst in the ester, as Just described, may comprise the phenyl alkyl amines such as phenyl ethanol amine, dicyclo hexyl amine, alkyl amines generally, and diphenyl amines and the like.

Quantities of acids and esters, such as described above, which are completely soluble in mineral oil have been found to render such oi1 entirely satisfactory to pass the ASTM rust test with synthetic sea water as required in the U. S. Navy Department, Bureau of Ships, Specification 14-0-15 for 2190 turbine oil. The following table shows the results of the ASTM rust test using a standard turbine oil containing various rust inhibiting additives:

As indicated above, the acid compound preferably has the general formula R-S- CH2) x-COOH where X is 1 to 4, preferably 1 or 2. A specific preferred formula is where R is an alkyl radical of 16 carbon atoms. As previously indicated, R ma be a hydrocarbon radical having from 10 to about 24 carbon atoms.

The limits of the present invention appear to be from 0.01 to 0.1% by weight of the alkyl thio monobasic acid composition, dissolved in mineral oil of appropriate viscosity. Lubricating grades will generally be found satisfactory. The alkyl radical has from 10 to 24 carbon atoms and the acid radica1 not more than 4 carbon atoms. To this composition is added from 0.01 to 5% by weight of the organic acid ester of polyhydric alcohol. The organic acid radical is preferably a fatty acid having from 12 to 22 carbon atoms, and may be saturated or unsaturated. The polyhydric alcohol radical may vary Widely in composition although it will preferably have a total of 2 to 16 carbon atoms. The complete ester ma vary in composition from the simple monooleate, monolaurate, etc., of a lower dihydric alcohol, such as ethylene glycol, to the tri-oleate, -stearate, etc., of nonamethylene glycol, decamethylene glycol, and like derivatives of related alcohols. The ester may thus have from about 12 or 14 to as many as about 80 carbon atoms.

It will be obvious that various esters and thio substituted acids may be combined, the general requisite being that the thio acid is at least slightly soluble in oil and has corrosion inhibiting properties in small quantities. Although we have specifically referred to the ester derived from ricinoleic acid in the examples given above, it will be obvious that the other esters described, such as derived from other fatty acids and other polyhydric alcohols may be equally useful.

We claim:

1. A rust preventing composition consisting essentially of mineral oil containing 0.01 to 0.1% by weight of a cetyl thioether of acetic acid, and 0.01 to 5% of polyethylene glycol hexaricinoleate.

2. A composition of the character described consisting essentially of a mineral oil containing 0.01 to 0.1% by weight of an alkyl thioether of a C2 to C4 saturated fatty acid wherein the etherifying radical is attached to a carbon atom outside the carboxyl group in said acid, said alkyl radical containing to 24 carbon atoms and 0.01 to 5% of a. C12 to C22 fatty acid ester of a polyhydric alcohol having from 12 to 80 carbon atoms.

3. A rust preventing composition consisting essentially of mineral oil containing 0.01 to 0.1% by weight of an alkyl thioether of acetic acid having 10 to 24 carbon atoms in the alkyl group and 0.01 to 5% of a polyhydric alcohol ester of a Cu to C22 fatty acid.

4. A rust inhibiting composition consisting essentially of a mineral oil of lubricating grade containing 0.01 to 0.1% by weight of a C10 to C24 alkyl thioether of a monobasic aliphatic acid containing not more than 4 carbon atoms in the acid radical, and 0.01 to 5% of a fatty acid ester of a polyhydric alcohol, said fatty acid radical having not less than 12 nor more than 22 carbon atoms.

5. A rust inhibiting composition consisting es sentially of a mineral lubricating oil containing about 0.03% by weight of cetyl thioether of acetic acid and 0.1% of polyethylene glycol hexaricinoleate.

6. A composition according to claim 4 which includes a suflicient quantity of a basic amine to neutralize any residual free acid catalyst present.

JONES I. WASSON. JOHN C. ZIMMER.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,216,751 Rosen Oct. 8, 1940 2,334,158 Fuchs et a1. Nov. 9, 1943 2,354,550 Rosen July 25, 1944 2,401,993 Wasson June 11, 1946 2,407,954 Fenske et a1. Sept. 17, 1946 2,412,633 Schwartz Dec. 17, 1946 

